The present invention pertains to an improved auxiliary transport device for sewing machines having a detaching knife disposed downstream of said auxiliary transport device and with a stretching means mounted slightly beyond said detaching knife for maintaining a partially sewn garment, hereinafter referred to as workpiece, in a stretched state and in alignment with the direction of the seam being formed.
Auxiliary transport devices are well known to those conversant in the art and serve the purpose of cooperating with the conventional main transport means or so-called feed dogs of the sewing machine to effect advancing and a desired stretching of a band being sewn onto partially sewn garments such as trousers, skirts and the like. Additionally the auxiliary transport device assists in maintaining the band in alignment with the direction of sewing so that on completion of the sewing cycle the band supply will be accurately cut with the cut edge extending perpendicular to said direction of sewing.
The more common type of known auxiliary transport and stretching devices are formed by roller elements having one-way releasable clutches which are caused to perform their function in synchronization with the sewing machine's main transport means. Other forms of auxiliary transport devices are also known such as endless belts which frictionally engage a workpiece as well as movable strips or chains which are disposed in alignment with the direction of sewing so as to effect advance of a workpiece through the cutting area that is provided with a conventional type detaching knife.
The customary manner of applying a band to a workpiece is that of providing a band source formed by one or more continuous strips of fabric. The band is guided by any suitable means so as to be attached to one edge of a leading workpiece of a series of workpieces disposed one in back of the other and with sufficient space between them to facilitate separation of the sewn workpiece after each sewing cycle.
This method of applying bands to workpieces is considered desirable for it increases production by minimizing the time intervals between each sewing cycle and can be attributed to the fact that the band source requires but a single mutual procedure of inserting the end thereof into a suitable guiding apparatus located forwardly of the sewing area. The band requires no further attention by the operator until the band supply or source is exhausted and requires replenishing.
The strip or strips comprising the band supply are usually pre-formed by cutting them from a large section of material or by forming it with shorter sections of the same material from which the workpieces are cut thereby assuring a matching combination when joined one to the other. When the band supply is formed from shorter sections of material, they are joined one to another to form a continuous strip which is fed or guided to the series of workpieces in the same manner described above which is also effective in minimizing the time interval between each sewing cycle.
With both forms of band supply the band must be subjected to a predetermined amount of tension and maintained in alignment with the direction of sewing so as to prevent misalignment of the seam being formed with the edge of the workpiece and cause the detaching cut to be made perpendicular to the edges of the sewn band.
Known types of auxiliary transport devices have performed their intended function with a degree of satisfaction, but require what is considered as an excessive amount of an operator's attention in maintaining a workpiece in alignment with the direction of sewing. This can be attributed to the size and weight of a workpiece for with the greater portion of the latter being located externally of the sewing zone, that portion in which the seam is being formed, has a natural tendency to pivot away from its intended direction of travel resulting in the formation of a seam displaced from the area of the workpiece where it was intended to be formed.
An object of the present invention is to provide an improved auxiliary transport device for sewing meachines which is capable of maintaining a workpiece in positive alignment with the direction of sewing during the complete sewing cycle without special attention on the part of an operator and which will provide a clean and accurate detaching cut at appropriate location on the workpiece at the completion of each said sewing cycle.